(1) Field of the Invention
The present invention relates to an optical switch using optical fibers. More particularly, the invention relates to a switch to be used for four optical transmission lines.
(2) Description of the Prior Art
In a configuration of a data transmission system in which a main station and several sub-stations are connected with one loop bus transmission line, a switch should inevitably be disposed to secure a signal line between two adjacent stations when troubles occur in the station or at the time of maintenance. As the switch to be used for this purpose, a switch in which the switching action performed by moving optical fibers directly attracts attention because it has a small size and the switching speed is high, and there has been proposed a switch in which optical fibers are arranged on the reed element of an electrical reed relay so as to render the optical fibers movable and switching is performed electro-magnetically.
Know switches of this type are of the one input-multiple output type, and when such switches are used for switching in four lines, there should inevitably be employed a pair of two switches of one input-two output type and as described in detail hereinafter, a disadvantage of the insertion loss is significant and causes a practically important problem.